Method for Decolorizing a Denim Fabric Using Ozone

ABSTRACT

This invention relates to a method for decolorizing a dyed denim fabric through a dry ozone process to obtain an aesthetically pleasing decolorized look or fashionably faded look in the denim fabric. The method comprises three dry ozone treatment processes used alone or in combination thereof. The first dry ozone treatment process includes wetting a denim textile product with water and oxidizing it with ozone. The second dry ozone treatment process includes spraying water to desired areas of the textile product and oxidizing it with ozone. The third dry ozone treatment process includes loading the denim textile product and wetted cotton fabric scraps into a drum, and oxidizing them with ozone.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Non-Provisional applicationSer. No. 13/746,144, filed Jan. 21, 2013, the entirety of which isincorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a method for decolorizing a denimfabric using ozone. More particularly, this invention relates to amethod for decolorizing a dyed denim fabric through a dry ozone processto obtain an aesthetically pleasing decolorized look or fashionablyfaded look in the denim fabric.

BACKGROUND OF THE INVENTION

Denim fabric has been decolorized to produce an aesthetically pleasingdecolorized look or fashionably faded look. Two major means used forsuch decolonization are stones and bleaches. Stones such as pumicestones are used to create a used and abused appearance in denim, fabricthrough a physical washing of the denim fabric with stones or rockshaving an abrasive surface. Alternatively, bleaches such as potassiumpermanganate, peroxide, or hypochlorite are used with or without stonesto decolorise or discolorize the surface of denim fabric.

FIG. 1 shows a conventional fabric decolorization method which comprisesa dry process S110, a desize process S120, an optional resin processS130, an abrasion process S140, a decolorization process S150, a localdecolorization process S160 and a finish process S170.

Dry process S110 is first performed on garments to achieve used or wornout look, and the dry process includes hand sand, whisker, grinding andlaser operation. After the dry process S110, the desize process S120 isconducted to remove starch from the raw fabric. In this process S120,enzymes such as amylase enzyme, lubricant and/or wetting may be appliedto the fabric and then, the fabric is rinsed. After the desize processS120, the resin process S130 may or may not be performed. The resinprocess S130 is to achieve three dimensional rigid look in the fabricand can be done by the processes of resin dip or spray, dry and resincure.

Then, the abrasion process S140 is conducted on the fabric using stone,superstone (like sand), and/or neutral enzyme, Then, the fabric isrinsed and dried. After the abrasion process S140, the decolorizationprocess S150 and the local decolonization process S160 are conducted onthe fabric. The decolonization process S150 is performed on the overallareas of the garments whereas the local decolonization process S160 isconducted on desired areas of the garments. Bleach or potassiumpermanganate is applied and then, the garments are neutralized usingchemicals such as sodium meta bisulfate.

Pumice stones are widely used for the abrasion process and adding pumicestones gives the additional effect of a faded or worn look, especiallyat the seam allowance or on stitches. The pumice abrades the surface ofthe garments like sandpaper, removing some dye particles from thesurfaces of the yarn.

Bleaching gives garments a more used look and brighter complexion and isusually carried out by strong oxidizing agents such as potassiumpermanganate, hypochlorite, or peroxide. Bleaching may be performed onthe garments in overall or selectively using a spray. Oxidation has tobe followed by neutralization because the remaining bleach will keep ondamaging the fabric.

Lastly, the finish process S170 is performed. Pocket white, softenerand/or tint may be applied to the garments. Laccase enzyme may be usedfor a special effect and rewashing with bleach or potassium permanganatefollowed by neutralization may be optionally conducted.

While the denim garments are decolorized, high quantities of indigo ayeare separated and they soil weft threads, inside pockets as well aslabels. To prevent this backstaining, pocket white is used to separateindigo. Pocket white may be applied in every treatment phase on thedenim fabric. The application of pocket white during stone washing orseparate after-washing leads to a reduction of the backstaining.

A number of problems have been presented by the use of stones and/orbleaches. First, the use of stones creates a considerable amount ofdamage to the denim products and the machine used for the stone washingprocess and a lot of time and labor have to be spent to remove stonesand rocks in pockets, creases, and interior folds of the garment and inthe machine. All the suspended solid of stone debris goes down to thewastewater and this makes it more costly to dump the wastewater to thesanitation system. Furthermore, the stone abrasion process is notselective and everything in the machines gets abraded whether it's agarment, a metal button or a rivet on the garments. This significantlyreduces the quality of the garments.

Besides, use of bleach or potassium, permanganate requires theneutralization, process because the remaining bleach or oxidative willcontinue to damage the garments and affect the shade and color of thegarments. Additionally, the use of bleach or potassium permanganate maycause environmental problems by increasing suspended solids and chemicaloxygen demand in wastewater as well as the volume of wastewater itself.These increases will lead to increased time and cost to treat wastewaterbecause suspended solids in wastewater always have to be treated andenvironmental regulations have put severe stress on the textile industryto control pollution by wastewater treatment and disposing of the usedpumice stones.

For the case of decolorizing t-shirts, there are several ways to dyet-shirts; direct dyeing, pigment dyeing, sulfur dyeing and reactivedyeing. Reactive dyeing uses a chemical reaction to dye a t-shirt.Stones or bleaches may be used to decolorize t-shirts if they are dyedby direct dyeing or pigment dyeing. Even if reactive dyeing producesvibrant colors of a t-shirt, there is no conventional way to decolorizet-shirts with reactive dyeing.

Accordingly, to solve the above problems, a need for a method fordecolorizing a dyed denim fabric through a dry ozone process to obtainan aesthetically pleasing decolorised look or fashionably faded look inthe denim fabric has been present for a long time considering theexpansive demands in the everyday lire. This invention is directed tosolve these problems and satisfy the long-felt need.

SUMMARY OF THE INVENTION

The present invention contrives to solve the disadvantages of the priorart.

An object of the invention is to provide a method for decolorizing adyed denim fabric through a dry ozone process to obtain an aestheticallypleasing decolorized look or fashionably faded look in the denim fabric.

Another object of the invention is to provide three dry ozone treatmentprocesses used alone or in combination thereof for decolorizing a dyeddenim fabric to obtain an aesthetically pleasing decolorized look orfashionably faded look in the denim fabric. The three dry ozonetreatment processes dispense with the need to use stones and bleachessuch as pumice stones or potassium permanganate. Furthermore, pocketwhite does not have to be used, either. With the three processes in use,stone washing, bleach washing and bleach spraying processes are notnecessary, but the same or better decolorized look or faded look ofgarments can be achieved by using the processes.

The first dry ozone treatment process includes wetting a denim textileproduct with water, removing excess water from the water-soaked denimtextile product, and exposing the denim textile product to the ozone gasfor decolorizing the textile product. The second dry ozone treatmentprocess includes spraying water to desired areas of the denim textileproduct and exposing the denim textile product to ozone gas todecolorize the textile product. Lastly, the third dry ozone treatmentprocess includes loading the denim textile product and cotton fabricscraps into a drum wherein the cotton fabric scraps are wetted withwater, supplying and stirring ozone gas inside the drum, and rotatingthe air-tight drum. The three dry ozone treatment processes may beapplied alone or in any combination thereof.

Still another object of the invention is to provide the three dry ozonetreatment, processes used alone or in combination thereof fordecolorizing a dyed t-shirts fabric to obtain an aesthetically pleasingdecolorized look or fashionably faded look in the t-shirts fabric. Therewas no conventional way to dye t-shirts with reactive dying, but thethree dry ozone treatment processes can achieve aesthetic decolorizationeffects even for t-shirts with reactive dying. Preferably, the third dryozone treatment process can achieve decolorization of t-shirts,especially at the hems.

The advantages of the present invention are: (1) the dry ozone treatmentprocesses of this invention dispense with the need to use stones andbleaches such as pumice stones or potassium permanganate, and thus theydo not create damages to the garments or machine, but improve thequality of the garments; (2) the dry ozone treatment processes of thisinvention reduce fabric treatment time and labor; (3) the dry ozonetreatment processes of this invention can create better and more variedaesthetically pleasing decolorized looks or fashionably faded looks inthe fabric; (4) the dry ozone treatment processes of this, inventionreduce the amounts of suspended solids and chemical oxygen demand inwastewater as well as the volume of wastewater itself; (5) the dry ozonetreatment processes of this invention can achieve aesthetically pleasingdecolorized looks or fashionably faded looks in t-shirts even withreactive dyeing; (6) the dry ozone treatment processes of this inventionuse less energy, water, labor, and process time than conventionalmethods using stones or bleaches; (7) the dry ozone treatment processesof this invention use less bleaches, harmful chemicals or potassiumpermanganate; and (8) the water used for ozone decolonization is mucheasier to recycle than waste water from the conventional methods.

Although the present invention is briefly summarized, the fullerunderstanding of the invention can be obtained by the followingdrawings, detailed description and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects and advantages of the presentinvention will become better understood with reference to theaccompanying drawings, wherein:

FIG. 1 is a flow chart showing a conventional fabric decolorizationmethod;

FIG. 2 is a flow chart showing the dry ozone treatment method of thepresent invention;

FIG. 3 is a flow chart showing the conventional abrasion process; and

FIG. 4 is a flow chart showing the ozone abrasion process of the presentinvention.

DETAILED DESCRIPTION EMBODIMENTS OF THE INVENTION

FIG. 2 shows the dry ozone treatment method of the present inventionusing the first dry ozone treatment process. Unlike the conventionalfabric decolorization method having three separate processes of abrasionprocess S140, decolorization process S150 and local decolonizationprocess S160, the present method has only one ozone treatment processS240. Furthermore, the finish process S250 has become a lot simpler.Especially, pocket white does not have to be used in the method of thisinvention,

There are three dry ozone treatment, processes for the ozonedecolorization process S240 of FIG. 2 and the three processes may beused alone or in any combination thereof for decolorizing a dyed fabricto obtain an aesthetically pleasing decolorized look or fashionablyfaded look in the fabric.

The first dry ozone treatment process includes wetting a textile productwith water, removing excess water from the water-soaked textile product,and exposing the textile product to the ozone gas for decolorizing thetextile product. The second dry ozone treatment process includesspraying water to desired areas of the textile product and exposing thetextile product to ozone gas to decolorize the textile product. Lastly,the third dry ozone treatment process includes loading the textileproduct and cotton fabric scraps into a drum wherein the cotton fabricscraps are wetted with water, supplying and stirring ozone gas insidethe drum, and rotating the air-tight drum. The three dry ozone treatmentprocesses may be applied alone or in any combination thereof.

The three dry ozone treatment processes dispense with the need to usestones and bleaches such as pumice stones or potassium permanganate.With the three processes in use, stone washing, bleach washing andbleach spraying processes are not necessary, but the same or betterdecolorized look or faded look of garments can be achieved by usingozone gas. Furthermore, pocket white does not have to be used eitherbecause there is less concern for backstaining.

The first dry ozone treatment process includes wetting a textile productwith water and thus, the process is not-selective. Thus, just likebleach washing, the whole wetted textile product is oxidized.

The second dry ozone treatment process includes spraying water todesired areas of the textile product and thus, only those desired areasare oxidized. This process can achieve the effect of bleach spraying.

The third dry ozone treatment process includes adding wetted cottonfabric scraps to dry garments. While the scraps and garments are rotatedinside a drum, the scraps provide water to random areas of the garmentsand the areas are oxidized. This process can achieve the effect of stonewashing.

Preferably, star fish patterns were achieved on the surface of thetextile product when all of the cotton fabric scraps is about or smallerthan 25 square inches, the weight ratio of the cotton fabric scraps towater is about 1.0:0.5˜1.5, and the weight ratio of the textile productto the cotton fabric scraps is about 1.0:0.2˜1.0. The ozone treatment isperformed for up to one hour.

FIG. 3 shows a conventional abrasion process S140 and FIG. 4 shows theozone abrasion process S340 of the present invention which is oneexample of the third dry ozone treatment process. The ozone abrasionprocess may be applied to a fabric, denim fabric or t-shirts. If appliedto t-shirts, stylish decoloration was achieved even if the t-shirts weredyed with reactive dyeing.

The ozone decolorizing method of the present invention comprises a dryprocess for manually treating a textile product; a desize process forremoving starch from the textile product; a step of wetting the textileproduct with water and removing: excess water from the water-soakedtextile product; a step of exposing the textile product to ozone gas fordecolorizing the textile product; and a step of washing the textileproduct with water and dehydrating the textile product. The step ofexposing the textile product to ozone gas may further comprise a step ofloading the textile product into a drum; a step of supplying andstirring ozone gas inside the drum; and a step of rotating the air-tightdrum.

Additionally, cotton fabric scraps may be loaded into the drum beforethe step of supplying and stirring ozone gas inside the drum wherein thecotton fabric scraps are wetted with water. Preferably, all of thecotton fabric scraps may be about or smaller than 25 square inches. Theweight ratio of the cotton, fabric scraps to water may be about1.0:0.5˜1.5 and the weight, ratio of the textile product to the cottonfabric scraps may be about 1.0:0.2˜1.0. Moreover, the ozone treatmentmay be performed for up to one hour.

Besides, the textile product may be denim or t-shirts.

Another ozone decolorization method of the present invention comprises adry process for manually treating a textile product; a desize processfor removing starch from the textile product; spraying water to desiredareas of the textile product; exposing the textile product to ozone gasto decolorize the textile product; rinsing the textile product; anddrying the textile product.

Before the step of supplying and stirring ozone gas inside the drum,wetted cotton fabric scraps may be loaded into the drum.

Still another ozone decolorization method of the present inventioncomprises a step of loading the textile product and cotton fabric scrapsinto a drum wherein the cotton fabric scraps are wetted with water; astep of supplying and stirring ozone gas inside the drum; a step ofrotating the air-tight arum; and a seep of washing the textile productwith water and dehydrating the textile product. Here, if the textileproduct is t-shirts, the desize process is not necessary.

While the invention has been shown and described with reference todifferent embodiments thereof, it will be appreciated by those skilledin the art that variations in form, detail, compositions and operationmay be made without departing from the spirit and scope of the inventionas defined by the accompanying claims.

What is claimed is:
 1. A Method for decolorizing a textile product,comprising: a step of loading the textile product and cotton fabricscraps into a drum wherein the cotton fabric scraps are wetted withwater; a step of supplying and stirring ozone gas inside the drum; astep of rotating the air-tight drum; and a step of washing the textileproduct with water and dehydrating the textile product.
 2. The methodfor decolorizing a textile product of claim 1 wherein the cotton fabricscraps are about or smaller than 25 square inches.
 3. The method fordecolorizing a textile product of claim 1 wherein the weight ratio ofthe cotton fabric scraps to water is about 1.0:0.5˜1.5 and the weightratio of the textile product to the cotton fabric scraps is about1.0:0.2˜1.0.
 4. The method for decolorizing a textile product of claim 1wherein the ozone treatment is performed for up to one hour.
 5. Themethod for decolorizing a textile product of claim 1 wherein the textileproduct is denim.
 6. The method for decolorizing a textile product ofclaim 1 wherein the textile product is t-shirts.